Add support for GLFW (#26)

Co-authored-by: Oliver Charles <ollie@ocharles.org.uk>

src/DearImGui/GLFW.hs

@@ -0,0 +1,51 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGui.GLFW
+
+GLFW specific functions backend for Dear ImGui.
+
+Modules for initialising a backend with GLFW can be found under the corresponding backend,
+e.g. "DearImGui.GLFW.OpenGL".
+-}
+
+module DearImGui.GLFW (
+    -- ** GLFW
+    glfwNewFrame
+  , glfwShutdown
+  )
+  where
+
+-- inline-c
+import qualified Language.C.Inline as C
+
+-- inline-c-cpp
+import qualified Language.C.Inline.Cpp as Cpp
+
+-- transformers
+import Control.Monad.IO.Class
+  ( MonadIO, liftIO )
+
+
+C.context (Cpp.cppCtx <> C.bsCtx)
+C.include "imgui.h"
+C.include "backends/imgui_impl_glfw.h"
+Cpp.using "namespace ImGui"
+
+
+-- | Wraps @ImGui_ImplGlfw_NewFrame@.
+glfwNewFrame :: MonadIO m => m ()
+glfwNewFrame = liftIO do
+  [C.exp| void { ImGui_ImplGlfw_NewFrame(); } |]
+
+
+-- | Wraps @ImGui_ImplGlfw_Shutdown@.
+glfwShutdown :: MonadIO m => m ()
+glfwShutdown = liftIO do
+  [C.exp| void { ImGui_ImplGlfw_Shutdown(); } |]